[nycphp-talk] MCrypt problems decrypting data

csnyder chsnyder at
Sat Aug 18 09:17:43 EDT 2007

On 8/18/07, csnyder <chsnyder at> wrote:
> You need to use the same initialization vector (IV) to decrypt as you
> did to encrypt. Typically, after encryption, you prepend the iv to the
> ciphertext value and store the whole thing (iv+encrypted). When you're
> ready to decrypt, you chop the iv off the front and use it to decrypt
> the ciphertext.
> Second, how are you generating the key? Is it a multiple of 32 characters long?

There's a nifty little class that will do this for you in the source
code for Pro PHP Security. See ch06-encryption/mcrypt.php:

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